Selenium-containing hydroprocessing catalyst, its use, and method of preparation

ABSTRACT

A hydroprocessing catalyst composition that comprises a support material and a selenium component and which support material further includes at least one hydrogenation metal component. The hydroprocessing catalyst is prepared by incorporating a selenium component into a support particle and, after calcination thereof, incorporating at least one hydrogenation metal component into the selenium-containing support. The metal-incorporated, selenium-containing support is calcined to provide the hydroprocessing catalyst composition.

This application claims the benefit of U.S. Provisional Application No.61/616,184, filed Mar. 27, 2012, which is incorporated herein byreference.

The invention relates to a selenium-containing hydroprocessing catalystcomposition, a method of making such composition, and the use of thecomposition in the hydroprocessing of hydrocarbon feedstocks.

In the catalytic hydroprocessing of hydrocarbon feedstocks catalystcompositions containing hydrogenation metals are used to promotedesulfurization and denitrogenation reactions to provide for the removalof organic sulfur and organic nitrogen compounds from the hydrocarbonfeedstocks. The reactions are accomplished by contacting catalystparticles with a hydrocarbon feedstock under conditions of elevatedtemperature and pressure and in the presence of hydrogen so that thesulfur components of the feedstock are converted to hydrogen sulfide andthe nitrogen components of the feedstock are converted to ammonia. Thehydrogen sulfide and ammonia may then be removed from the treatedhydrocarbon to give a hydrotreated product.

Typical hydroprocessing catalysts contain one or more hydrogenationmetals supported on a porous refractory oxide support material. Thehydrogenation metal is usually selected from metals of Group VIII of theperiodic table, such as nickel and cobalt, and Group VI of the periodictable, such as molybdenum and tungsten. The porous refractory oxidesupport material can typically be alumina. Promoters such as phosphorousmay also be used as a component of the hydroprocessing catalyst.

The prior art discloses many types of hydroprocessing catalysts andprocesses. One example of a prior art catalyst is disclosed in U.S. Pat.No. 5,389,595. In this patent, a catalyst is presented that contains anoverlayer of a catalytic promoter, such as a Group VIB metal, on aporous refractory support that contains an underbedded Group VIII metalcontaining component. The catalyst may also contain additional catalyticpromoter materials that include phosphorus, titanium, zirconium,hafnium, vanadium, manganese, magnesium, calcium, lanthanum, copper,Group VIB metals, and Group VIII metals. The catalyst typically containsgreater than 4.0 weight percent of Group VIII metal component(calculated as the monoxide) and greater 10 weight percent of Group VIBmetal component (calculated as the trioxide). The phosphorus componentis typically present in the catalyst from about 0.5 to about 15 weightpercent (calculated as P). The '595 patent does not disclose the use ofselenium as a component of its catalyst composition nor does it disclosea catalyst composition having an underbedded selenium component. Therealso is no indication that selenium may be used to improve theperformance of hydroprocessing catalysts.

Another example of a hydroprocessing catalyst is disclosed in U.S. Pat.No. 7,871,513. The catalyst presented in this patent is a calcinedmixture made by calcining a formed particle of a mixture comprisingmolybdenum trioxide, a nickel compound, and an inorganic oxide material.The mixture may have less than 2 weight percent of a molybdenum compoundother than molybdenum trioxide, an amount of molybdenum trioxide so asto provide a molybdenum content in the calcined mixture in the rangeupwardly to 12 weight percent, and an amount of nickel compound so as toprovide a nickel content in the calcined mixture that is in the rangeupwardly to 4 weight percent. The '513 patent does not disclose the useof selenium as a component of its catalyst composition nor does itdisclose a catalyst composition having an underbedded seleniumcomponent. There is no indication presented in the '513 patent thatselenium may be used to improve the performance of hydroprocessingcatalysts.

It is an important and continuing aim of the industry to discover anddevelop hydroprocessing catalysts of improved activity. Catalysts ofimproved activity allow for the operation of hydrotreating reactorsunder milder process conditions resulting in lower energy requirementsto yield the desired products and longer catalyst life due to lower cokeformation.

Accordingly, provided is the inventive hydroprocessing catalyst thatcomprises a support particle comprising an inorganic refractory oxideand a selenium component. The support particle further has incorporatedin it at least one hydrogenation metal component.

Another invention is directed to a method of making a hydroprocessingcatalyst by preparing a support comprising an inorganic refractory oxideand incorporating a selenium component into the support particle toprovide a selenium-containing support. The selenium-containing supportis calcined to provide a calcined selenium-containing support into whicha hydrogenation metal is incorporated to provide a metal-incorporated,selenium-containing support that is further calcined to provide thehydroprocessing catalyst.

The inventive hydroprocessing catalyst or an hydroprocessing catalystprepared by the inventive method of making such a catalyst may be usedin a hydrotreating process that comprises contacting under hydrotreatingprocess conditions a hydrocarbon feedstock with the hydroprocessingcatalyst.

A method is also presented that provides for the improvement in certainof the catalytic properties of a hydroprocessing catalyst including aninorganic refractory oxide support and at least one hydrogenation metalcomponent, wherein the method comprises: incorporating a seleniumcomponent into the inorganic refractory oxide support.

FIG. 1 presents a plot of the relative weight activity of a number ofcatalyst compositions as a function of the weight percent selenium thatis contained in each respective catalyst.

A novel catalyst composition has been discovered that exhibits enhancedhydrodesulfurization activity over other prior art compositions. Itfurther is found that significant improvements are achieved in thecatalytic activity of a hydroprocessing catalyst by the incorporation orintroduction of a selenium component into its support material.

The catalyst composition of the invention, in general, comprises asupport material, a selenium component and at least one hydrogenationmetal component. The support material used in the preparation of theinventive catalyst composition may be selected from a group of porousinorganic refractory oxide materials that can suitably provide a supportfor the metal hydrogenation components of the catalyst composition ofthe invention.

Examples of possible suitable porous refractory oxides that may be usedinclude silica, alumina, titania, zirconia, silica-alumina,silica-titania, silica-zirconia, titania-alumina, titania-zirconia,zirconia-alumina, and combinations of two or more thereof. The preferredporous refractory oxide for use in the preparation of the supportmaterial of the composition of the invention is one selected from thegroup consisting of alumina, silica, and silica-alumina. Among these,the more preferred porous refractory oxide is alumina. A particularlypreferred alumina support material is wide pore alumina.

The porous refractory oxide generally may have an average pore diameterin the range of from about 50 Angstroms (Å) to about 350 Angstroms (Å)with a significant portion of the pores having pore diameters in therange of from 100 Å to 350 Å. The total pore volume of the porousrefractory oxide as measured by standard mercury porosimetry methods isin the range of from about 0.2 cc/gram to about 2 cc/gram. The surfacearea of the porous refractory oxide, as measured by the B.E.T. method,generally exceeds about 100 m²/gram, and it is typically in the range offrom about 100 to about 400 m²/gram.

In the preparation of the inventive composition, the selenium compoundor component typically can be combined with the support material by anysuitable means or method so as to provide a support particle comprisingthe support material and the selenium component. Thus, the seleniumcomponent may be comulled with the support material during thepreparation of a mixture that is formed or shaped into support particlesof the composition, or the selenium component may be incorporated by anysuitable means or method into an already formed or shaped inorganicrefractory oxide support particle. An example of a suitable method forincorporating the selenium component into the support particle is by anypore volume impregnation known to those skilled in the art. As isdiscussed herein, the incorporation of the selenium component into thesupport material of a hydroprocessing catalyst can provide for ahydroprocessing catalyst, including an inorganic refractory oxidesupport and at least one hydrogenation metal component, having certainenhanced catalytic properties.

Any suitable selenium containing compound capable of providing for theinventive composition having desired properties may be used in itspreparation. Examples of possible suitable selenium compounds that maybe incorporated into or mixed with the support material include selenatecompounds, such as selenate salts, e.g., selenic acid (H₂SeO₄), andselenite compounds, such as selenite salts, e.g., selenous acid(H₂SeO₃). Other possible selenium compounds include the oxides ofselenium, such as, selenium dioxide and selenium trioxide, and theselenium compounds of selenium tetrachloride (SeCl₄), seleniumtetrafluoride (SeF₄), selenium oxybromide (SeOBr₂), seleniumoxydichloride (SeOCl₂), selenium disulfide (SeS₂), selenium hexasulfide(Se₂S₆), selenoyl fluoride (SeO₂F₂), and selenium monochloride (Se₂Cl₂).The preferred selenium compound for use in preparing the inventivecomposition and providing for the selenium component of the inventivecomposition is either selenous acid or selenic acid, and, among these,selenous acid is the more preferred.

In one embodiment of the invention, a support particle, comprising aninorganic refractory oxide, such as, for example, alumina, is firstprepared and then followed by incorporation of the selenium compoundinto the support particle. The support particle of the catalystcomposition is, typically, in the form of an agglomerate or a shapedparticle. The support material, thus, is formed into a particle or shapeby any of the suitable means or methods known to those skilled in theart.

Typically, in the preparation of a shaped support, the porous refractoryoxide starting material is in the form of a powder and is mixed withwater, and, if desired or necessary, other chemical aids such aspeptizing agents or flocculating agents or binders or other compounds,to form a mixture, which may be an extrudable paste, that is formed intoan agglomerate or shaped particle. It particularly can be desirable toextrude the mixture that is in the form of an extrudable paste to makeextrudates of any one or more of various shapes such as cylinders,trilobes, quadralobes, and etc. having nominal sizes such as 1/16 inch,⅛ inch, 3/16 inch, and etc.

The agglomerate or shaped particle that comprises one or more of thepreviously listed inorganic oxide compounds is then dried to give adried shaped support particle that is used in the preparation of theinventive catalyst composition. Drying of the shaped support particle iscarried out under standard drying conditions that can include a dryingtemperature in the range of from 50° C. to 200° C., preferably, from 75°C. to 175° C., and, more preferably, from 90° C. to 150° C. Typically,this drying step is done in the presence of oxygen or anoxygen-containing gas air.

The dried support particle typically will include upwardly to 100 weightpercent, on a dry basis, inorganic refractory oxide. Generally, theamount of inorganic refractory oxide of the dried support particle is inthe range of from 80 wt. % to 100 wt. %, and, more typically theinorganic refractory oxide is present in an amount in the range of from90 wt. % to 100 wt. %.

In a preferred embodiment of the invention, the support particle, whichmay be in the form of a shaped particle, e.g., an extrudate, a sphere, apill, etc., is dried, but not calcined, prior to the incorporation ofthe selenium compound or component into the support particle. It isbelieved that the incorporation of the selenium compound or componentinto the dried-only support particle, prior to its calcination,ultimately provides for a final hydroprocessing catalyst composition ofthe invention that has certain enhanced properties over those of ahydroprocessing catalyst composition made by utilizing a supportparticle that has been calcined prior to incorporation therein of theselenium component.

While not wanting to be bound to any particular theory, it is thoughtthat by incorporating the selenium into the uncalcined shaped supportparticle followed by calcination of the selenium-containing support, theselenium participates in some important but unknown way in the chemicaltransformation that takes place when the inorganic refractory oxidechanges its crystalline form due to the high temperature calcination. Anexample of such a transformation is when an inorganic refractory oxidesuch as alumina changes from the pseudo boehmite form that it ispredominantly in before calcination treatment to the gamma form uponcalcination treatment.

Thus, in one embodiment of the invention, the support particle,comprising a porous refractory oxide, before the incorporation thereinof the selenium compound, may undergo a drying treatment, but not acalcination treatment, to provide a dried-only selenium-containingsupport particle. Therefore, the drying treatment of the supportparticle is carried out at a drying temperature that is less than acalcination temperature. In this case, the drying temperature should notexceed 350° C., and, preferably, the drying temperature at which thesupport particle is dried does not exceed 300° C., and, most preferably,the drying temperature does not exceed 250° C.

After the selenium compound is incorporated into the dried-only supportparticle, the resulting selenium-containing support is then calcinedunder standard calcination conditions that include a calcinationtemperature in the range of from 250° C. to 900° C., preferably, from300° C. to 800° C., and, most preferably, from 350° C. to 600° C. Thiscalcination step provides a calcined selenium-containing support(calcined support).

The calcined selenium-containing support particle comprises, consistsessentially of, or consists of an inorganic refractory oxide, which ispreferably alumina, and a selenium component. It is desirable for theselenium component to be present in the calcined support particle at aconcentration in the range of from an effective concentration upwardlyto or about 3 weight percent (wt. %) based on the dry weight of theinorganic refractory oxide of the calcined support particle andcalculated based on the selenium as the element.

It is noted that a small concentration of selenium in the calcinedsupport can provide for a final hydrotreating catalyst composition thathas significantly enhanced hydrotreating catalytic activity whencompared against similar hydrotreating catalysts made with a calcinedsupport that has no material or effective concentration of selenium. Itfurther has been discovered that incremental increases in the seleniumconcentration of the calcined support are attributable to incrementalincreases in catalytic activity of the final hydroprocessing catalystcomposition but that there is an optimum in the improvement in catalyticactivity. Therefore, there is a maximum selenium concentration of thecalcined support at which point there is no more observed incrementalimprovement in the catalyst activity with incremental increases in theselenium concentration. From this maximum selenium concentration level,incremental increases in the selenium concentration in the calcinedsupport tend to result in incremental decreases in catalytic activityuntil the catalyst activity becomes the same as or less than theactivity of the comparative catalyst which uses a calcined support thatcontains no material concentration of selenium.

It is, thus, generally desirable for the selenium component of thecalcined support, i.e., the calcined selenium-containing support whichcomprises, consists essentially of, or consists of an inorganicrefractory oxide and a selenium component, to be present therein at amaterial or effective concentration that typically can be in the rangeof from or about 0.01 wt. % to or about 2.95 wt. %, based on the dryweight of the inorganic refractory oxide of the calcined supportparticle and calculated based on the selenium as the element, regardlessof its actual form. A preferred selenium concentration within thecalcined support is in the range of from or about 0.05 wt. % to or about2.85 wt. %, and, a more preferred selenium concentration is in the rangeof from 0.075 wt. % to 2.75 wt. %.

It is also a preferred feature of the inventive catalyst composition forthe selenium component to be an underbedded selenium component. What ismeant when referring herein to an underbedded selenium component is thatthe selenium is incorporated into the porous inorganic refractory oxidematerial of the support particle that is thereafter calcined, underconditions described herein, to provide the calcined selenium-containingsupport onto which at least one hydrogenation metal component isintroduced as an overlayer of hydrogenation metal. Thismetal-incorporated, selenium-containing support is then calcined undersuitable calcination conditions, as described herein, to provide theinventive catalyst composition having an underbedded selenium componentwith an overlayer of at least one hydrogenation metal component.

To prepare the hydroprocessing catalyst of the invention, at least onehydrogenation metal component is incorporated as a metal overlayer intothe calcined selenium-containing support particle. The hydrogenationmetal may be incorporated into the calcined support particle, comprisingan inorganic refractory oxide and a selenium component, by any suitablemeans or method known to those skilled in the art, but the preferredmethod of incorporation is by any of the well known pore fillimpregnation procedures.

The calcined support particle therefore is impregnated by one or moreimpregnation steps with at least one hydrogenation metal component usingone or more aqueous solutions containing at least one metal salt whereinthe metal compound of the metal salt solution is an active metal oractive metal precursor. The metal elements are those selected from GroupVI of the Periodic Table of the elements (e.g., chromium (Cr),molybdenum (Mo), and tungsten (W)) and Group VIII of the Periodic Tableof the elements (e.g., cobalt (Co) and nickel (Ni)). Phosphorous (P) mayalso be a desired metal component.

For the Group VIII metals, the metal salts include Group VIII metalacetates, formats, citrates, oxides, hydroxides, carbonates, nitrates,sulfates, and two or more thereof. The preferred metal salts are metalnitrates, for example, such as nitrates of nickel or cobalt, or both.

For the Group VI metals, the metal salts include Group VI metal oxidesor sulfides. Preferred are salts containing the Group VI metal andammonium ion, such as ammonium heptamolybdate and ammonium dimolybdate.

The phosphorus compounds that may be used include the acids ofphosphorus, such as meta-phosphoric acid, pyrophosphoric acid, andphosphorous acid. The preferred phosphorus compound is orthophosphoricacid (H₃PO₄), or a precursor of an acid of phosphorus, i.e., aphosphorus-containing compound capable of forming a compound containingat least one acidic hydrogen atom when in the presence of water, such asphosphorus oxide, phosphorus, or the like.

The concentration of the metal compounds in the impregnation solution(metal-containing impregnation solution) is selected so as to providethe desired metal content in the final hydroprocessing catalystcomposition of the invention taking into consideration the pore volumeof the calcined support into which the aqueous solution is impregnated.Typically, the concentration of metal compound in the impregnationsolution is in the range of from 0.01 to 100 moles per liter.

The amount of metal incorporated into the calcined selenium-containingsupport to provide a metal-impregnated, selenium containing support maydepend upon the application in which the composition of the invention isto be used, but, generally, for the hydroprocessing applicationscontemplated herein, the Group VIII metal component, i.e., cobalt ornickel, preferably, nickel, can be present in the final hydroprocessingcatalyst in an amount in the range of from 0.5 wt. % to 20 wt. %,preferably from 1 wt. % to 15 wt. %, and, most preferably, from 1.5 wt.% to 12 wt. %.

The Group VI metal component, i.e., molybdenum or tungsten, preferably,molybdenum, can be incorporated into the calcined selenium-containingsupport in an amount such that final hydroprocessing catalyst has aconcentration of Group VI metal component in the range of from 5 wt. %to 50 wt. %, preferably from 7.5 wt. % to 40 wt. %, and, mostpreferably, from 10 wt. % to 30 wt. %.

When the final hydroprocessing catalyst contains a concentration ofphosphorus, the amount of the phosphorus component that is incorporatedinto the calcined selenium-containing support is such that the finalhydroprocessing catalyst has a phosphorus content in the range ofupwardly to or about 5 wt. %, and, typically, from 0.1 wt. % to 5 wt. %.The preferred concentration of the phosphorus component of thehydroprocessing catalyst is in the range of from or about 0.3 wt. % toor about 4 wt. %, and, more preferably, the range is from 0.5 wt. % to 3wt. %.

The above-referenced weight percents for the metal components andphosphorus are based on the weight of the total dry weight of thehydroprocessing catalyst and the metal and phosphorus, if present,components being in an oxide form regardless of their actual form, e.g.,the oxide form or sulfide form or elemental form, of the metalcomponent.

In the preparation of the catalyst composition of the invention, themetal-containing impregnation solution may be an aqueous solutioncomprising at least one metal, as described above, having ahydrogenation function, and the aqueous solution may further,optionally, comprise phosphorus. The at least one metal of themetal-containing impregnation solution may include, for example, a metalselected from the group consisting of nickel, cobalt, molybdenum,tungsten and any combination of two or more thereof. The metal componentand, optionally, the phosphorus component, is incorporated into thecalcined support to thereby provide a metal-incorporated,selenium-containing support, or an impregnated support.

The incorporation of the metal-containing impregnation solution into thecalcined support may be done by any suitable means or method known tothose skilled in the art. One such method may include standardimpregnation by incipient wetness or even soaking the calcined supportwith an excess amount of the metal-containing impregnation solution thanwould otherwise be used in a dry impregnation or an incipient wetnessimpregnation. The metal-incorporated support undergoes a drying stepunder drying conditions as detailed earlier herein.

After the metal is incorporated into the calcined selenium-containingsupport, the resulting metal-incorporated, selenium-containing supportor impregnated support is dried and then calcined under standardcalcination conditions that include a calcination temperature in therange of from 250° C. to 900° C., preferably, from 300° C. to 800° C.,and, most preferably, from 350° C. to 600° C. The calcination istypically conducted in an air or oxygen atmosphere. This calcinationstep provides the final hydroprocessing catalyst of the invention.

In hydrotreating applications, the inventive hydroprocessing catalyst iscontacted under suitable hydrodesulfurization conditions with ahydrocarbon feedstock that typically has a concentration of sulfur.

The more typical and preferred hydrocarbon feedstock is a petroleummiddle distillate cut having a boiling temperature at atmosphericpressure in the range of from or about 140° C. (284° F.) to or about410° C. (770° F.). These temperatures are approximate initial andboiling temperatures of the middle distillate.

Examples of refinery streams intended to be included within the meaningof middle distillate include straight run distillate fuels boiling inthe referenced boiling range, such as, kerosene, jet fuel, light dieseloil, heating oil, heavy diesel oil, and the cracked distillates, such asFCC cycle oil, coker gas oil, and hydrocracker distillates. Thepreferred feedstock of the inventive distillate hydrodesulfurizationprocess is a middle distillate boiling in the diesel boiling range offrom about 140° C. to 400° C.

The sulfur concentration of the middle distillate feedstock can be ahigh concentration, for instance, being in the range upwardly to about 2weight percent of the distillate feedstock based on the weight ofelemental sulfur and the total weight of the distillate feedstockinclusive of the sulfur compounds. Typically, however, the distillatefeedstock of the inventive process has a sulfur concentration in therange of from 0.01 wt. % (100 ppmw) to 1.8 wt. % (18,000). But, moretypically, the sulfur concentration is in the range of from 0.1 wt. %(1000 ppmw) to 1.6 wt. % (16,000 ppmw), and, most typically, from 0.18wt. % (1800 ppmw) to 1.1 wt. % (11,000 ppmw).

It is understood that the references herein to the sulfur content of thedistillate feedstock are to those compounds that are normally found in adistillate feedstock or in the hydrodesulfurized distillate product andare chemical compounds that contain a sulfur atom and which generallyinclude organosulfur compounds.

The hydroprocessing catalyst composition of the invention may beemployed as a part of any suitable reactor system that provides forcontacting it or its derivatives with the distillate feedstock undersuitable hydrodesulfurization conditions that may include the presenceof hydrogen and an elevated total pressure and temperature.

Such suitable reaction systems can include fixed catalyst bed systems,ebullating catalyst bed systems, slurried catalyst systems, andfluidized catalyst bed systems. The preferred reactor system is thatwhich includes a fixed bed of the inventive hydroprocessing catalystcontained within a reactor vessel equipped with a reactor feed inletmeans, such as a feed nozzle, for introducing the distillate feedstockinto the reactor vessel, and a reactor effluent outlet means, such as aneffluent outlet nozzle, for withdrawing the reactor effluent or thetreated hydrocarbon product or the ultra-low sulfur distillate productfrom the reactor vessel.

The hydrodesulfurization process generally operates at ahydrodesulfurization reaction pressure in the range of from 689.5 kPa(100 psig) to 13,789 kPa (2000 psig), preferably from 1896 kPa (275psig) to 10,342 kPa (1500 psig), and, more preferably, from 2068.5 kPa(300 psig) to 8619 kPa (1250 psig).

The hydrodesulfurization reaction temperature is generally in the rangeof from 200° C. (392° F.) to 420° C. (788° F.), preferably, from 260° C.(500° F.) to 400° C. (752° F.), and, most preferably, from 320° C. (608°F.) to 380° C. (716° F.).

The flow rate at which the distillate feedstock is charged to thereaction zone of the inventive process is generally such as to provide aliquid hourly space velocity (LHSV) in the range of from 0.01 hr⁻¹ to 10hr⁻¹.

The term “liquid hourly space velocity”, as used herein, means thenumerical ratio of the rate at which the distillate feedstock is chargedto the reaction zone of the inventive process in volume per hour dividedby the volume of catalyst contained in the reaction zone to which thedistillate feedstock is charged.

The preferred LHSV is in the range of from 0.05 hr⁻¹ to 5 hr⁻¹, morepreferably, from 0.1 hr⁻1 to 3 hr⁻¹ and, most preferably, from 0.2 hr⁻¹to 2 hr⁻¹.

It is preferred to charge hydrogen along with the distillate feedstockto the reaction zone of the inventive process. In this instance, thehydrogen is sometimes referred to as hydrogen treat gas. The hydrogentreat gas rate is the amount of hydrogen relative to the amount ofdistillate feedstock charged to the reaction zone and generally is inthe range upwardly to 1781 m³/m³ (10,000 SCF/bbl). It is preferred forthe treat gas rate to be in the range of from 36 m³/m³ (200 SCF/bbl) to1781 m³/m³ (10,000 SCF/bbl), more preferably, from 44 m³/m³ (250SCF/bbl) to 1602 m³/m³ (9,000 SCF/bbl), and, most preferably, from 53m³/m³ (300 SCF/bbl) to 1425 m³/m³ (8,000 SCF/bbl).

The desulfurized distillate product yielded from the process of theinvention has a low or reduced sulfur concentration relative to thedistillate feedstock. A particularly advantageous aspect of theinventive process is that it is capable of providing a deeplydesulfurized diesel product or an ultra-low sulfur diesel product. Asalready noted herein, the low sulfur distillate product can have asulfur concentration that is less than 50 ppmw or any of the other notedsulfur concentrations as described elsewhere herein (e.g., less than 15ppmw, or less than 10 ppmw, or less than 8 ppmw).

The following examples are presented to further illustrate theinvention, but they are not to be construed as limiting the scope of theinvention.

EXAMPLE I Selenium Doped Support

This Example I describes the preparation of each of the supports used inthe preparation of the inventive and comparative compositions. Thevarious embodiments of the inventive compositions described in theseexamples include the use of an alumina support that contains aconcentration of selenium.

An alumina extrudate was prepared by mulling a wide pore alumina powderwith from 1 to 3.5 wt % nitric acid and enough water to produce a finalmixture having an loss on ignition (LOI) value in the range of from 58to 62 wt %. The mulling of the components was for a time period of fromabout 15 to 20 minutes. The final mixture was extruded into a 1.3 mmtrilobe shape and pellets of a length of around 5 mm. These extrudateswere then dried at a temperature of 125° C. (257° F.) for about 3 to 4hours. The dried extrudates were not calcined before the incorporationof the selenium component as described below.

The dried-only, uncalcined alumina extrudate was pore-fill impregnatedwith an aqueous solution of selenous acid (H₂SeO₃). The selenous acidsolution was prepared by dissolving selenous acid in water with heatingto 88° C. (190° F.).

After the impregnation of the extrudate, the selenium-impregnatedextrudate was dried at a temperature of 125° C. (257° F.) for 2 hoursand then calcined in air at 482° C. (900° F.) for 1 hour to provide acalcined selenium-containing extrudate.

Four different supports were used in the preparation of the finalcatalyst compositions described in Examples II and III. The support usedin the preparation of the base or comparison compositions contained noselenium as a dopant. The other three supports were each impregnatedwith a different concentration levels of selenium. The following Table 1presents the amounts of selenium used in the preparation of each of thefour supports by weight parts H₂SeO₃ per 100 weight parts of dried-only,uncalcined alumina extrudate.

TABLE 1 Selenium levels in each support Wt. H₂SeO₃ per 100 wt dried onlyalumina Support extrudate A 0 B 0.442 C 2.19 D 4.37

EXAMPLE II Catalyst Composition

This Example II describes the preparation of catalyst compositions usingan acid side prepared metals impregnation solution to impregnate theselenium-containing supports of Example I.

To prepare the metals impregnation solution, a first solution was madein a first beaker by introducing into the first beaker 7.11 g of waterfollowed by 6.15 g of ammonium dimolybdate (57.5% Mo) and 3.45 g ofmolybdenum oxide (62.5% Mo) while stirring. Next, 1.49 g of 30% hydrogenperoxide was added to the contents of the first beaker followed by theslow addition of 0.85 g monoethanol amine while keeping the temperatureof the mixture below 60° C. (140° F.). The mixture was maintained at atemperature in the range of from 49-60° C. (120-140° F.) with stirringuntil clear solution was formed. Afterwards, the clear solution wascooled to room temperature.

A second solution was prepared by placing into a second beaker 1.58 gwater, 3.07 g 86.8% H₃PO₄ and 3.95 g nickel nitrate (20.19% Ni). Thismixture was heated to a temperature of 32° C. (90° F.) while beingstirred. 1.32 g NiCO₃ (40.24% Ni) was added to this mixture slowly, inorder to control the foaming, and the resulting mixture was heated to35° C. (95° F.) until it was clear. The clear solution was then cooled.

The first solution and the second solution were mixed together and thevolume of the mixture of two solutions was adjusted to 24.2 ml with theaddition of water.

To impregnate the selenium doped supports of Example I, 30 g of therelevant selenium-containing extrudate (i.e., A, B, C and D) was placedinto a polyethylene container (bottle) with an appropriate amount of themetal impregnation solution that is described above in this Example II.The bottle was then capped and gently shaken to aid in the impregnation.The metals-impregnated, selenium-containing support was aged for atleast 2 hrs, dried for 3 hrs at 125° C., and then calcined at 482° C.(900° F.) for 1 hr. The resulting catalyst composition contained 13.5 wt% Mo, 3.15 wt % Ni, and 2 wt % P. The following Table 2 presents theweight percent selenium in each of the four catalyst compositionsprepared by the method described in this Example II.

TABLE 2 Selenium concentration of each catalyst composition WeightSupport- Percent Catalyst Selenium A-1 0 B-2 0.23 C-3 1.1 D-4 2.15

EXAMPLE III Catalyst Composition

This Example III describes the preparation of catalyst compositionsusing a standard prepared metals impregnation solution to impregnate theselenium-doped supports of Example I.

To prepare the metals impregnation solution, 24.7 g of water wasintroduced into a beaker followed by the addition of 3.36 g of 86.8%phosphoric acid, 9.817 g of molybdenum oxide (62.5% Mo), and 3.001 g ofnickel hydroxide (58% Ni) while the beaker contents were stirred. Themixture was heated to 190° F. held until there was a clear solution. Thesolution was then cooled to room temperature, and the volume wasadjusted to 24.2 ml by the addition of water.

To impregnate the selenium doped support of Example 1, 30 g of therelevant selenium-containing extrudate was placed into a polyethylenecontainer (bottle) with an appropriate amount of the metals impregnationsolution described above in this Example III. The bottle was then cappedand gently shaken to aid in the impregnation. The metals-impregnated,selenium-containing support was aged for at least 2 hrs, dried for 3 hrsat 125° C., and then calcined at 482° C. (900° F.) for 1 hr. Theresulting catalyst composition contained 14.1 wt % Mo, 4 wt % Ni and 2.1wt % P. The following Table presents the weight percent selenium in eachof the four catalyst compositions prepared by the method described inthis Example III.

TABLE 3 Selenium concentration of each catalyst composition WeightSupport- Percent Catalyst Selenium A-5 0 B-6 0.22 C-7 1.06 D-8 2.08

EXAMPLE IV Catalyst Activity Testing

This Example IV describes the hydrodesulfurization activity testing ofeach of the six selenium containing catalysts (Catalysts B2, C3, D4, B6,C7, and D8) and the two comparison catalysts (Catalysts A1 and A5).Activity test data is also presented.

Each of the batch reactors were loaded with 80 mg of one of the eightcatalysts. The catalysts were then sulfided by pressurizing the reactorswith a 5% H₂S/95% hydrogen gas to 300 psi followed by raising thereactor temperature to 350° C. A gas flow rate of 120 cc/min and reactortemperature of 350° C. were maintained for 3 hrs. The reactors were thencooled to room temperature and purged with nitrogen gas.

After the sulfiding of the catalysts, the reactors each were then loadedwith 3.95 g of distillate feed on top of the sulfided catalysts andre-pressurized with 100% hydrogen gas to 300 psi. The reactortemperature was raised to 340° C. and held constant for 2 hours whilemaintaining during this time a gas flow rate 100 cc/min. The reactorswere then cooled to room temperature and the remaining sulfurconcentrations in the feeds were tested. The remaining sulfurconcentrations of the feeds were used to calculate the catalystactivities per milligram. The performance of each catalyst was thennormalized to that of a commercially available hydrodesulfurizationcatalyst. The resulting measured catalyst activities of the eight testedcatalysts are expressed as relative weight activity (RWA) versuscommercial catalyst and are presented in the following Tables 4 and 5.

TABLE 4 Selenium concentration of each catalyst composition WeightSupport- Percent Catalyst Selenium RWA A-1 0 1.25 B-2 0.23 2.1 C-3 1.11.8 D-4 2.15 1.5

TABLE 5 Selenium concentration of each catalyst composition WeightSupport- Percent Catalyst Selenium RWA A-5 0 1.3 B-6 0.22 1.58 C-7 1.061.75 D-8 2.08 1.2

As may be observed from an examination of the relativehydrodesulfurization activity values that are presented in Tables 4 and5, the catalyst compositions prepared using a selenium-doped aluminasupport that has a small but material concentration of a seleniumcomponent show a significant increase in their relative weight activity(RWA) for the desulfurization of a distillate feedstock compared to theRWA of the catalyst composition using the support containing noselenium. Presented in FIG. 1 are plots of the data contained in Tables4 and 5. It appears from the data presented that the RWA of the catalystcontinues to improve as the selenium concentration of the selenium-dopedalumina support increases from zero and then the RWA reaches a maximumimprovement. At this point, the RWA of the catalyst declines withfurther increases in the selenium concentration of the selenium-dopedsupport until there is, instead of an improved activity, a worstcatalytic performance than that of the catalyst that uses a supportcontaining no selenium. Thus, there appears to be an optimum seleniumconcentration in the doped support that provides for enhanced catalyticactivity.

That which is claimed is:
 1. A method of making a hydroprocessingcatalyst, wherein said method comprises: preparing a support particle,comprising an inorganic refractory oxide; incorporating a seleniumcompound into said support particle to provide a selenium-containingsupport; calcining said selenium-containing support to provide acalcined selenium-containing support, comprising said inorganicrefractory oxide and a selenium component; incorporating a hydrogenationmetal into said calcined selenium-containing support to provide ametal-incorporated, selenium-containing support, comprising saidinorganic refractory oxide and a selenium component; and calcining saidmetal-incorporated, selenium-containing support to provide saidhydroprocessing catalyst, wherein said hydroprocessing catalyst includesa concentration of said Group VIII metal component in saidhydroprocessing catalyst in the range of from 0.5 wt. % to 20 wt. %based on the total weight of said hydroprocessing catalyst andcalculated based on the Group VIII metal component as an oxide, andwherein said hydroprocessing catalyst includes a concentration of saidGroup VI metal component in said hydroprocessing catalyst in the rangeof from 5 wt. % to 50 wt. % based on the total weight of saidhydroprocessing catalyst and calculated based on the Group VI metalcomponent as an oxide.
 2. A method as recited in claim 1, wherein saidsupport particle is uncalcined prior to said incorporating of saidselenium compound into said support particle.
 3. A method as recited inclaim 2, wherein said calcined selenium-containing support has aconcentration of a selenium component therein in the range upwardly to 3weight percent based on the dry weight of said inorganic refractoryoxide and calculated based on said selenium component as the element. 4.A method as recited in claim 3, wherein said hydrogenation metalcomprises at least on hydrogenation metal component that includes aGroup VIII metal component of either a nickel component or a cobaltcomponent and a Group VI metal component of either a molybdenumcomponent or a tungsten component.
 5. A composition prepared by any oneof the methods of claims 1 through
 4. 6. A method as recited in claim 4,wherein said calcining of said selenium-containing support to providesaid calcined selenium-containing support is conducted at a firstcalcination temperature in the range of from 250° C. to 900° C.
 7. Amethod as recited in claim 6, wherein said calcining of saidmetal-incorporated, selenium-containing support is conducted at a secondcalcination temperature in the range of from in the range of from 250°C. to 900° C.
 8. A method as recited in claim 7, wherein saidconcentration of said selenium component is in the range of from 0.075wt. % to 2.75 wt. %, said concentration of said Group VIII metalcomponent is in the range of from 1.5 wt. % to 12 wt. %, and saidconcentration of said Group VI metal component is in the range of from10 wt. % to 30 wt. %.
 9. A method as recited in claim 1, wherein saidcalcining of said selenium-containing support to provide said calcinedselenium-containing support is conducted at a first calcinationtemperature in the range of from 250° C. to 900° C., and wherein saidcalcining of said metal-incorporated, selenium-containing support isconducted at a second calcination temperature in the range of from inthe range of from 250° C. to 900° C.
 10. A method as recited in claim 9,wherein said concentration of said selenium component is in the range offrom 0.075 wt. % to 2.75 wt. %, said concentration of said Group VIIImetal component is in the range of from 1.5 wt. % to 12 wt. %, and saidconcentration of said Group VI metal component is in the range of from10 wt. % to 30 wt. %.